In an internal-combustion engine, a timing drive system synchronously transmits rotation from the crankshaft to the camshaft in the case of a single overhead cam (SOHC) engine, and from the crankshaft to both camshafts in a double overhead cam or twin cam (DOHC) engine. Most recent automobile engines are DOHC engines. These timing drives can include chain drives, in which power is transmitted by a chain wrapped around sprockets, and toothed belt drives, in which power is transmitted by a toothed belt wrapped around toothed pulleys.
A chain drive in a DOHC engine, comprises camshaft sprockets respectively secured to two camshafts, and a crankshaft sprocket secured to a crankshaft. Similarly, a toothed belt timing drive comprises toothed pulleys secured respectively to two camshafts, and a toothed pulley secured to a crankshaft. In both cases, the timing drive synchronously transmits rotation from the crankshaft to the camshafts at a ratio of 2:1. Each of these timing drive systems also comprises other parts such as a tensioner, a tensioner lever, a chain or belt guide, and the like.
In the process of assembling a timing drive, each of the several parts must be properly mounted and secured at the appropriate position on the engine. Problems have arisen, especially when a worker forgets to mount a particular part. Moreover, the conventional timing drive assembly process requires a significant amount of time, and is therefore costly.
One approach to solving these problems is described in published British patent application 2347174. In this approach, parts, such as a crankshaft sprocket, camshaft sprockets, a timing chain, a guide rail, a tensioner lever, and a tensioner, are assembled on first and second cover parts to provide a completed assembly, which can be mounted on an engine.
Similar problems arise in the case of a bicycle, where parts such as a pedal sprocket, a rear wheel sprocket, and a chain, are separately prepared and independently mounted and secured at appropriate positions on the bicycle in the assembly process. In the assembly of a bicycle drive, as well as in the assembly of an engine's timing drive, the mounting and securing of parts requires significant time and is therefore costly. There is also a risk that parts will be forgotten. In the case where the parts are stored and transported to an assembly location, it is frequently necessary to take the troublesome step of packaging the parts together as a set. Moreover, the sizes of the parts can vary where different engines or different bicycles are being produced, and in such a case, there is a risk of mounting an improper part.
Furthermore, in the pre-assembled timing transmission described in British patent application 2347174, since the timing transmission is accommodated in a case composed of first and second cover parts, the cost of the assembly is relatively high, problems of oil sealing and sound insulation arise, and there is also the problem of making cases that accommodate the shapes and sizes of different engines.
The principal object of this invention is to provide a parts retaining panel that can be transported while parts are retained thereon in their final arrangement, so that the parts can be readily and easily mounted and secured in the process of assembly of a machine such as a bicycle or internal combustion engine, and so that forgetting to mount parts can be avoided. It is also an object of the invention to provide an advantageous method of mounting and securing parts in the assembly of a drive such as a bicycle drive or the timing drive of an internal combustion engine.